%!TEX TS-program = xelatex
%!TEX encoding = UTF-8 Unicode

\documentclass[11pt,tikz,border=1]{standalone}
\usepackage[default]{cjkfonts}

\begin{document}
  \begin{tikzpicture}[
    neuron/.style={circle,draw,inner sep=0pt,minimum size=8mm}
    ]

    % leftmost perceptrons:
    \node (pl1) at (-2.25, 1.25) [neuron] {};
    \node (pl2) at (-2.25, 0) [neuron] {};
    \node (pl3) at (-2.25, -1.25) [neuron] {};

    % middle perceptrons:
    \node (pm1) at (0, 1.875) [neuron] {};
    \node (pm2) at (0, 0.625) [neuron] {};
    \node (pm3) at (0, -0.625) [neuron] {};
    \node (pm4) at (0, -1.875) [neuron] {};

    % rightmost perceptron:
    \node (pr) at (2.25, 0) [neuron] {};

    % output:
    \node (output) at (5.5, 0) {\ $output + \Delta output$};

    \node (weight) at (-1.125, 2.5) {$w + \Delta w$};

    % connect nodes:

    \draw [->] (pl1) to (pm1);
    \draw [->] (pl1) to (pm2);
    \draw [->] (pl1) to (pm3);
    \draw [->] (pl1) to (pm4);
    \draw [->] (pl2) to (pm1);
    \draw [->] (pl2) to (pm2);
    \draw [->] (pl2) to (pm3);
    \draw [->] (pl2) to (pm4);
    \draw [->] (pl3) to (pm1);
    \draw [->] (pl3) to (pm2);
    \draw [->] (pl3) to (pm3);
    \draw [->] (pl3) to (pm4);
    \draw [->] (pm1) to (pr);
    \draw [->] (pm2) to (pr);
    \draw [->] (pm3) to (pr);
    \draw [->] (pm4) to (pr);
    \draw [->] (pr) to (output);

    \draw (weight) -- node [above] {
      \begin{tabular}{c}
        \footnotesize 任何权重（或偏置）中的微小改变 \\
        \footnotesize 引起一个输出的微小改变
      \end{tabular}
    } (6.35, 2.5);
    \draw [->] (6.35, 2.5) -- (6.35, 0.25);

    % \draw [->] (weight) -- node (5.5, 2.5) to (output);

  \end{tikzpicture} 
\end{document}
